Insulin does a lot of important things for us. It pulls glucose from the blood and fritters it away into our cells to be burned for energy or stored as glycogen. It prevents hyperglycemic toxicity[1] to neurons, pancreatic cells, the arterial walls and the generation of excessive levels of reactive oxygen species. It even promotes muscle protein synthesis[2] and helps augment muscular hypertrophy, especially following resistance training. Clearly, we need insulin. Without it, we’d die, as type 1 diabetics readily do without an exogenous source.

But insulin has other effects, like inhibiting the breakdown of body fat into free fatty acids for energy production. Although locking fatty acids into body fat sounds terrible, it isn’t evidence of insulin being malicious. Lipolysis is temporarily blunted so that we can burn or sequester the glucose coming in. Once the glucose is handled, lipolysis resumes. We oscillate between fat burning and glucose burning, seamlessly switching fuel sources when needed. Sure, we’re not burning any fat when insulin is elevated, but once our insulin levels normalize we’ll be back on track. When you’re insulin sensitive, this is pretty much how it works. You secrete enough insulin to get the job done, but not so much that you gain weight and stop burning fat.

What if a person secretes too much insulin in response to a glucose load? What if, for whatever reason (and there are dozens of possible culprits), a person’s cells are resistant to the effects of insulin? What if, to remove the same amount of glucose from the blood, a person secretes twice or thrice the amount of insulin? What happens when insulin stays elevated? Lipolysis is inhibited to an even greater degree. Body fat becomes even harder to burn. Susceptible brain, artery, and pancreatic cells are exposed to higher levels of blood sugar for longer. Muscle protein synthesis falls off a cliff. Glycogen is replenished at a diminished rate. And if cells are already full of glycogen and there’s nowhere else to put the glucose, it converts to fat for storage.

Obviously, we don’t want to be insulin resistant. We want to be insulin sensitive. But how do we do it?

1. Lift weights.

Lifting heavy things, particularly with great intensity, improves insulin sensitivity by an interesting mechanism: non-insulin dependent glucose uptake happens immediately after the workout, which allows your muscles to replenish glycogen without insulin. According to some researchers[3], “the effect of exercise is similar to the action of insulin on glucose uptake.” I’d say not having to secrete any insulin makes you effectively insulin-sensitive.

2. Run (or bike/swim/row) sprint intervals.

An overloaded, energy-replete cell is an insulin resistant cell. An empty, “starving” cell is an insulin sensitive cell. Any exercise that burns glycogen and leaves your muscles empty and gaping for more will necessarily increase insulin sensitivity. I can’t think of a faster way to burn through your glycogen than with a high intensity interval training session[4]. Hill sprints[5] or rower sprints are sufficiently intense and comprehensive.

3. Do CrossFit or similar full body high-volume, high-intensity training.

Glycogen depletion occurs locally: high rep leg presses will deplete leg muscle glycogen[6], but they won’t touch glycogen in your arms, chest, and back. To fully deplete all the glycogen, you need to do full-body movements. CrossFit WODs and other similar metcon workouts that have you doing pullups[7], squats[8], sprints, pushups[9], box jumps, and other compound movements — at high volume, in the same workout, and with minimal rest—will drain your glycogen stores and reduce the amount of insulin you need to replenish them.

4. Train at altitude.

A recent study[10] found that altitude hiking at 4500 meters improved glucose tolerance and insulin sensitivity. This isn’t feasible for everyone (4500 meters is really quite high, and not everyone lives near a suitable mountain), and some people just aren’t ready to climb a mountain and hike around (in the study, some participants with low DHEA-S levels didn’t get the benefits), but it’s one way to improve it. Just google around to see if any local hikes reach those heights.

5. Train fasted.

While training of any kind promotes better insulin sensitivity, training in the fasted state enhances this effect. One study[11] found that relatively high-intensity “cardio” performed while fasted increased subjects’ insulin sensitivity beyond the group who did the same training after a carb meal, even in the context of a normally obesogenic high-fat, high-carb diet.

7. Never stop exercising.

I don’t mean “take no breaks.” I mean “stay active for life.” In a recent paper, both sprinters (aged 20-90 years) and endurance athletes (20-80 years) had far better insulin sensitivity than sedentary controls. And get this: insulin sensitivity didn’t decrease with age in the two active groups[17]. Even the 90 year-old sprinter retained good insulin sensitivity. The sedentary controls? Not so much.

9. Sprinkle some vinegar on your food.

Next time you plan on eating a high-carb meal, have a salad with a vinegar-based dressing[21] beforehand. Vinegar has been shown[22] to increase insulin sensitivity in response to a carb-rich meal in type 2 diabetics.

16. Go hug someone you love.

Okay, so maybe the researchers didn’t prescribe bear hugs to improve insulin sensitivity in overweight subjects. Maybe they used intranasal oxytocin[42]. But oxytocin is what we secrete in response to positive social interactions like sex[43], good conversation, dinner parties, breastfeeding, and yes, hugs.

I’ve been telling you guys to get on this stuff for awhile now. No more messing around, yeah? A natto (sticky stinky fermented soybeans) breakfast improves insulin sensitivity[54]. Long-fermented kimchi also improves[55] it; fresh kimchi does, too, but not as much as the sour stuff.

21. Cook with ginger and garlic.

Cook with ginger and garlic because they’re delicious. Cook with ginger and garlic because many dishes require their inclusion. But also cook with ginger and garlic because both can improve insulin sensitivity. Ginger helped[57] type 2 diabetics regain insulin sensitivity and glucose tolerance. Garlic helped[58] fructose-fed rats do the same.

24. Reduce refined sugar intake.

Some would say “reduce all sugar intake.” That’s a mistake, because it eliminates many colorful fruits and berries, most of which either have a neutral or beneficial effect on insulin sensitivity. But by most accounts, eating excessive amounts of refined sugar (and perhaps even moderate amounts[63]) can reduce insulin sensitivity[63]. And “excessive” is relative, of course. Highly active individuals with room to spare in their glycogen compartments have more leeway. I still do sugar[64] in my coffee, and I’ll have a bite or two of dessert if someone else orders it at dinner.

25. Eat liver and oysters once a week.

Ruminant liver and oysters are some of the best sources of copper and zinc, two minerals that play essential roles in maintenance of insulin sensitivity. Serum zinc and copper have inverse relationships to insulin resistance[65], and increases in zinc status match up well[66] with improvements to insulin sensitivity. If you absolutely hate these foods, you can certainly find zinc and copper elsewhere. These are just the quickest way to obtain them (plus other important nutrients).

Now, this isn’t an exhaustive list. There are probably other ways to improve insulin sensitivity outlined in the literature, and still others yet to be discovered. But this is a good start that should keep you busy for a good long while.

Now, let’s hear from you guys. What did I miss that should be included? What shouldn’t be included? What’s worked for you? What didn’t that everyone said would?

Thanks for reading!

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